# 5.2.4 Circles, PT3 Focus Practice

 
               
Question 10:
 
Diagram below shows two quadrants, AOC and EOD with centre O.
 
 
 Sector AOB and sector BOC have the same area.
 Calculate the area, in cm2, of the coloured region.
                     
 
 Solution:
               
 
 
 
  
         
Question 11:
  
The Town Council plans to build an equilateral triangle platform in the middle of a roundabout. The diameter of circle RST is 24 m and the perpendicular distance from R to the line ST is 18 m. as shown in Diagram below.
  Find the perimeter of the platform.
  

  Solution:
  

  Given diameter = 24 m
  hence radius = 12 m
  O is the centre of the circle.
  Using Pythagoras’ theorem: